3/4 HP enough for RF30 on VFD?

Newer inverter rated 1750 RPM motors can easily be run up to 2X their base speed so 120 Hz, Hp is constant above 60Hz but torque falls off, below 60 Hz torque is flat and the Hp decreases in a linear fashion down to 0. Although the torque is flat, if you decrease the speed to 30 Hz you loose the mechanical advantage of the pulleys so you are still loosing 50% of the torque at the spindle. When you over speed the motor you gain the mechanical advantage of the lower speed pulley ratio. Most factory inverter rated mills are direct drive and run their motor from something like 20-200 Hz. Some inverter/vector motors like the Marathon BlackMax will spin to 6000 RPM. Standard inverter motors will easily run in the 100-120Hz and typically maintain full Hp. Cooling becomes an issue unless you have an electric blower or a TENV motor.

When you setup your VFD you want to run it in sensroless vector mode which can boost the low speed torque at the lower speeds. If buying a generic Chinese VFD then many people with buy up to the next size so a 3 Hp VFD to run a 2 Hp motor. If you go with something like a Teco L510 or Hitachi NE-S1 you just need to match the motor amps to the VFD rated output amps.
 
Looks to be a real good choice. I assume 3 hp from amps, can't read it.

You could run that one from 10 hz to 120 hz. on a VFD
 
its 1.5 HP $75 new but I will have to do some mods to fit that odd frame

How do you know it will take 10-120hz?
 
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OK, I was wrong on Hp. You probably won't be able to run it down that low. Experience on the machine will tell you the bottom.

As far as top end, there is debate on how high you can turn them up. My thinking, the inside of a 2 pole motor (3600 RPM) is built exactly like a four pole (1800) so there is no reason not to spin them that fast or 120 hz. I actually go for more - 150 hz - and have never had an issue. I've done this for years with my 5 hp marathon motor on my 10EE.
 
Try to find a 6 pole motor, nominal speed will be around 1200 RPM. Its especially useful on machines without back gearing. I have 1 HP 6 pole with VFD on my Rockwell mill, works out really nice.
 
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